Rates of intact perineum
Seven trials involving 2143 women were included in this outcome, 2129 women contributed data. The result of meta-analysis indicated that women in lubricant group had no statistically difference in the incidence of intact perineum when compared with those in standard care group (RR 1.22, 95%CI 0.99 to 1.50; I2=75%; very low certainty due to serious risk of bias, serious inconsistency and serious imprecision) (Table 1, Figure S22).
Subgroup analyses based on lubricants type and overall risk of bias were not significant subgroup effect (Pinteraction=0.40 and Pinteraction=0.22, respectively) (Figure S23, Figure S24). The heterogeneity of obstetric gel groups and high risk of bias groups was significantly reduced after subgroup analysis (I2=40% and I2=0%, respectively), while significant heterogeneity remained within liquid wax groups and low high risk of bias groups (I2=69% and I2=86%, respectively). This heterogeneity might partially result from studies of liquid wax and low high risk of bias (Figure S23, Figure S24).
The result analyzed based on parity indicated that there was significant in the rate of intact perineum in lubricant group versus standard care group for nulliparous women (RR 1.18, 95%CI 1.04 to 1.33; I2=0%) (Figure S25). There was insufficient data to perform subgroup analysis for this outcome for multiparous women.